# Pertaining to The Martian, what is the ratio of SOLs to Earth days?

I didn't see an explanation in the movie. How many days pass on Earth when one SOL passes on Mars?

I heard a reference of two months passing, but I thought only (counts)....less than 50 SOLs had passed.

The physics of Mars in The Martian is identical to the actual physics of the planet, as such, we only need to know the actual length of a Martian sol (in hours/minutes) to know how it compares with an Earth day.

A Martian day is nearly identical to an Earth day. There's only a difference of about 2.7% between the two.

The average length of a Martian sidereal day is 24h 37m 22.663s (88,642.66300 seconds based on SI units), and the length of its solar day (often called a sol) is 24h 39m 35.244147s (88,775.244147 seconds). The corresponding values for Earth are 23h 56m 4.0916s and 24h 00m 00.002s, respectively. This yields a conversion factor of 1.02749125170 days/sol. Thus Mars' solar day is only about 2.7% longer than Earth's.

The number above you're interested in is the solar day - 24 hours, 39 minutes, 35 seconds.

• Isn't the number they are interested in 1.02749125170 since they are looking for the ratio? as in 1:1.02749125170 – Puddler Jan 12 '17 at 5:13
• "There's only a difference of about 2.7% between the two." Not to humblebrag, but I had a great opportunity to work on a Mars mission when I was in college (my avatar photo is from this mission). A difference of "only" 40 minutes/day for a 90 sol mission meant that every sol's work begins at 8:00am, then 8:40am, ..., 8:00pm, etc. I lived in 3 straight months of perpetual jet lag. Great experience, but would not want to repeat shifting my schedule daily by 40 minutes! – Dang Khoa Jan 12 '17 at 6:45
• @DangKhoa for some people (most notably 'evening people'), the increased day length is actually beneficial. – Glorfindel Jan 12 '17 at 10:30
• I need to create calories. And I need enough to last the 1387 sols until Ares 4 arrives. If I don’t get rescued by Ares 4, I’m dead anyway. A sol is 39 minutes longer than a day, so it works out to be 1425 days. - from Chapter 3, `LOG ENTRY: SOL 25` – Gallifreyan Jan 12 '17 at 11:18